This invention relates to machine readable documents and reading methods, and in particular relates to a method for embedding machine readable data in a document.
Paper documents constitute the fundamental medium for distribution of information. They are economical, easy to use and ubiquitous. While networks of electronically stored documents play a valuable role in modern business, the continuing role of paper documents cannot be denied.
A large number of paper documents are issued and processed by enterprises and government units every year.
To facilitate easy movement of information from an electronic record to paper and back, it is possible to print machine readable data on paper documents. For instance, barcodes are commonly used for encoding machine readable data on paper as they offer high data density and incorporate error correction techniques.
Machine readable data can be affixed to documents in a number of ways depending on factors such as target data density, ruggedness and aesthetic requirements of the document. Appending 2D barcodes such as PDF417 barcodes to a document is a well known technique for offering machine readability to paper documents. The PDF417 (portable data file 417) format is a stacked linear bar code symbol used in a variety of applications, including transport, identification cards, and inventory management.
However, several of the known techniques require the division of the paper document into two parts: one part for the human readable material exclusively and the other for machine readable data. Each part of the paper document can thereby carry only one channel of information. Restricting machine readable data to a small and separate area reduces the data carrying capacity.
Another technique for embedding data on paper is to print low density machine readable markings over the entire printable area of the paper and superimpose human readable material on the machine readable marking.